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Since its opening in 1959, the St. Lawrence Seaway has provided a route into the Great Lakes not only for trade, but also unfortunately for aquatic invasive species (AIS) that have had severe economic and environmental impacts on the region. Prevention measures have been introduced by the governments of Canada and the United States, but reports of newly discovered AIS continue, and only time will tell what impacts these species may have. Pressure to solve the problem has even led to proposals that the Seaway be closed. At the request of the Great Lakes Protection Fund, the National Research Council assembled a committee of experts to identify and explore options that would both enhance the potential for global trade in the Great Lakes region and eliminate further introductions of aquatic invasive species from ships transiting the St. Lawrence Seaway. This report concludes that trade should continue on the St. Lawrence Seaway but with a more effective suite of prevention measures that evolves over time in response to lessons learned and new technologies.

Key Messages

Closing the seaway to transoceanic shipping would reduce substantially the risk of AIS introductions by vessels using the waterway, this action could not, in the committee's judgment, be implemented in a timely fashion. Moreover, economic principles indicate that eliminating a transportation option would increase the cost of moving goods and therefore would not enhance trade.

In the committee's judgment, such a measure would achieve a high level of protection against further ship-vectored AIS introductions without the disadvantages of closing the seaway to transoceanic shipping, if it was supported by effective procedures for vessel monitoring and for enforcing ballast water management regulations and by an AIS surveillance and control program for the Great Lakes.

Mandatory use of ballast water management technologies by all categories of vessel known to pose a risk could lead to a marked reduction in AIS introductions by vessels using the seaway and could be implemented almost immediately.

Because of the number, diversity, and distribution of vectors and routes by which AIS can enter the Great Lakes, the committee views elimination of all new AIS introductions as virtually impossible.

Two very different alternatives were identified: (a) use ballast water management technologies (ballast water exchange, saltwater flushing, and ballast water treatment) to kill or remove organisms in ships' ballast water or (b) close the seaway to the riskiest component of traffic from an AIS perspective, namely, transoceanic vessels engaged in trade with countries outside of Canada and the United States.